Some transmission type image display apparatuses including liquid crystal display apparatuses use direct-type surface light source apparatuses as a backlight. In recent years, direct-type surface light source apparatuses having a plurality of light emitting diodes (LEDs) as a light source have come into use.
For example, a direct-type surface light source apparatus includes a substrate, a plurality of LEDs, a plurality of light flux controlling members (expanding lens) and a light diffusion member (diffusion panel). The plurality of LEDs are arranged in a matrix shape on the substrate. Above each LED, the light flux controlling member that expands light emitted from each LED in a surface direction of the substrate is arranged. The light emitted from the light flux controlling member is diffused by the light diffusion member, and illuminates an illumination target member (for example, a liquid crystal panel) in a planar shape.
Patent Literature 1 discloses manufacturing a light flux controlling member (expanding lens) used for a direct-type surface light source apparatus by injection molding using a transparent resin. Further, Patent Literature 1 discloses utilizing a gate protrusion (side gate) formed, by injection molding, on an outer peripheral part of an emission surface for positioning of the light flux controlling member.